The Reaction of Hydrochloric Acid with Sodium Bicarbonate
C11-3-10, 14 & 15
Introduction:
We’re all fascinated with the reaction of baking soda with acids such as
acetic acid (used in vinegar), sulfuric acid (used in battery acid) or
hydrochloric acid (stomach acid). The reaction between the acid and the
baking soda has obvious common uses such as the neutralization of acids in
our stomach or on our clothes. As well the reaction of baking soda and acids
was used as a form of carbon dioxide production in fire extinguishers for the
extinguishing of fires. More recently this type of fire extinguisher has
received considerable media attention:
Fire Extinguisher Is Banned by City
By UNITED PRESS INTERNATIONAL
Published: January 21, 2003
City officials yesterday announced a ban on the use of old-fashioned
inverted ''soda acid'' fire extinguishers because the devices could
explode and injure someone trying to use them. Officials said
''thousands'' of the brass-cased extinguishers are still housed at
schools and other buildings.
A Fire Department spokesman, John Mulligan, said the department
had not used the extinguishers since their manufacture was halted in
1969. Tests that year showed the canisters, which contain sulfuric
acid and sodium bicarbonate, could cause injuries.
Comptroller Harrison J. Goldin's Office of Risk Management asked
for a ban on the use of the extinguishers after a firefighter who was
injured using one last year filed a $600,000 suit against the city. The
ban, which carries a fine of up to $600, is expected to take effect in
two weeks. The canisters should be turned in to the Fire Department
for destruction.
1
Pre-laboratory Information:
In this laboratory exercise we are going to explore the stoichiometric
relationship between an amount of reacting solid sodium bicarbonate and the
amount of solid product it produces.
a) Write a word equation for the reaction of solid sodium bicarbonate
and a solution of hydrochloric acid:
b) Express this as a balanced chemical equation
c) Look at the following web-link to witness what will occur in this
reaction at the molecular level
Go to: http://www.dlt.ncssm.edu/TIGER/chem2.htm
Click on: DoubleDisp_Reaction-GasProduction.html
d) The reaction shows there are three products. What are they?
e) How can you experimentally isolate the dissolved sodium chloride
from the other two products?
Procedure:
In this experiment you will need:
sodium bicarbonate
tongs for heating test tube
small beaker (50 mL)
spatula
1 boiling (test) tube
balance with 0.01 gram precision
safety goggles
eyedropper
3-5 M hydrochloric acid
1. Put on your safety goggles.
2. Collect a boiling tube and weigh. Record this weight in the chart that
follows.
2
2. Using a spatula add to the test tube enough baking soda to fill the curved
bottom of the test tube.
3. Reweigh the test tube recording the mass of contents and test tube. Again
record this weight.
4. Calculate the mass of sodium bicarbonate and record in table.
5. Collect in a beaker a small amount of hydrochloric acid and eyedropper.
Warning: Hydrochloric acid is caustic and corrosive. Avoid contact and
immediately rinse any acid that comes in contact with your skin or
clothes.
6. To the test tube add drop-by-drop hydrochloric acid to the baking soda.
What evidence (list two) is there for a reaction occurring?
a)
b)
7. Continue to add acid carefully until the reaction stops. Note that at this
stage all of the sodium bicarbonate particles have been consumed. Based on
the chemical reaction equation discussed earlier at this stage:
a) what products are present in the test tube?
b) what reactant(s) are still in the test tube?
STOP: At this point in the lab the teacher will demonstrate the proper
method for heating and boiling liquids.
8. Evaporate off the fluid (water) in the test tube. Gently heat the fluid
above the flame. There must be no eruption or spurting of fluid out of
your test tube. Proceed until dry. What product remains?
9. Remove the test tube from the flame and test for water vapor by inverting
a clean dry test tube over the mouth of the test tube. If you see condensation
all water has not escaped from the test tube. Continue to heat the test tube to
ensure all water has been driven off.
3
10. Let the test tube cool.
11. Reweigh the test tube and record final mass.
12. Finally, determine the mass of solid that remains.
13. Clean up all of your equipment as indicated.
Results:
1. Mass of test tube
2. Mass of test tube and sodium
bicarbonate
3. Mass of sodium bicarbonate
4. Mass of test tube and final
contents (sodium chloride)
5. Mass of sodium chloride
6. Moles of sodium bicarbonate
reacting
7. Moles of sodium chloride
produced
8. Experimental mole ratio of
sodium chloride to sodium
bicarbonate
9. Theoretical mole ratio of sodium
chloride to sodium bicarbonate
Analysis:
1. Write the balanced equation for this reaction between hydrochloric acid
and sodium bicarbonate.
2. Note that in this equation the coefficient for both the sodium
bicarbonate and hydrochloric acid is 1. Thus the theoretical mole
ratio for this reactant and product is 1:1. Enter this ratio in the chart
above in 9. At the particle level what does this mean is occurring in the
chemical reaction?
4
3. Calculate the number of moles of sodium bicarbonate consumed in this
reaction. Show all your work.
4. Calculate the number of moles of sodium chloride produced in this
reaction. Show all your work.
5. How does the experimental number of moles of sodium bicarbonate
consumed compare to the experimental number of moles sodium
chloride produced? That is, compare these experimental mole ratios.
How do they compare? Enter this value in the table in 8 above.
6. Calculate the theoretical yield of sodium chloride that should have been
produced from the mass of sodium bicarbonate used in the reaction. This
will require you to (1) change mass of reactant to moles of reactant, (2)
then look at the mole ratio to determine the number of moles and (3)
finally convert moles of product to mass of product (sodium chloride)
formed?
7. Compare the actual yield with your calculated theoretical yield. Are they
close? By what percentage of the expected result are you off?
8. What factors may have contributed to any experimental error.
9. In your own investigation what was the limiting reagent (hydrochloric
acid or sodium bicarbonate) and why?
5
10.What is meant by a “reaction going to completion”?
11.Explain at the molecular level why the balanced chemical equation is so
important in determining experimental yield.
12. In your own words explain why in the calculation process for theoretical
yield we determined mass of the reactant (sodium bicarbonate), then
moles of reactant, then looked at the mole ratio to determine the number
of moles and mass of product (sodium chloride) formed? In other words,
why don’t we just deal with masses?
13. In the old fire extinguishers the reactants (sodium bicarbonate and
sulfuric acid) were placed in a brass-cased container. Research to find out
how these were constructed to ensure the reactants only reacted when the
extinguisher was needed. Draw an illustration of this mechanism below.
14. Finally, what is the chemical and mechanism of today’s home fire
extinguishers? Why are these much safer equipment than the old sodaacid fire extinguishers?
6